This longitudinal study approaches child development through the analysis of autonomic function, cognitive processing, and socioemotional expression at 2, 5, 13, 20, and 36 months in healthy term infants. In relation to these areas, specific behaviors of the mother (autonomic, intellectual, and interactional) are examined. A combination of physiological assessment, psychometric measurement, and observational techniques is utilized to examine comprehensively the roles of cognitive processing and socioemotional expression in early child development.